I have a Trademarked Hallmark, and it is not cheap. It is possible to do it yourself, without a lawyer, but expect headaches and pages of legaleeze to dredge through. Also, there is no part of government in the US that will police trademarks or copyrights for you. Expect to do this yourself. Your trademark is only as secure as your wallet will allow. Even deep pockets like Tiffanys can't stop the knockoffs being sold under their logo, even in department stores like Macy's. This is also why you will see many big name brands being sold at flea markets. It just costs a lot of money to take these scumbags to court and fight them year in and year out on a single case. And, there is no monetary gain from the lawsuits, as most of the counter-fitters don't have money, or declare bankruptcy as soon as they lose.
So that said, mine cost me about a thousand, and I went as cheaply as possible. That is just legal fees to my lawyer, who did it for me cheaply.
Of course as soon as mine was done, I had Chinese repos of some of my designs hitting the flea markets, and since I couldn't afford to hire detectives to trace behind the vendors nor legal fees to pay the lawyers to enforce it, it was a waste of money. So... do what you want. :::sigh:::